This webinar brought to you by the Relion product family Relion
This webinar brought to you by the Relion® product family Advanced protection and control IEDs from ABB Relion. Thinking beyond the box. Designed to seamlessly consolidate functions, Relion relays are smarter, more flexible and more adaptable. Easy to integrate and with an extensive function library, the Relion family of protection and control delivers advanced functionality and improved performance. © ABB Group October 7, 2014 l Slide 1 ABB Protective Relay School Webinar Series Disclaimer ABB is pleased to provide you with technical information regarding protective relays. The material included is not intended to be a complete presentation of all potential problems and solutions related to this topic. The content is generic and may not be applicable for circumstances or equipment at any specific facility. By participating in ABB's web-based Protective Relay School, you agree that ABB is providing this information to you on an informational basis only and makes no warranties, representations or guarantees as to the efficacy or commercial utility of the information for any specific application or purpose, and ABB is not responsible for any action taken in reliance on the information contained herein. ABB consultants and service representatives are available to study specific operations and make recommendations on improving safety, efficiency and profitability. Contact an ABB sales representative for further information. © ABB Group October 7, 2014 l Slide 2 ABB Protective Relay School Webinar Series Line distance protection fundamentals Elmo Price October 7, 2014 Presenter Elmo Price received his BSEE from Lamar State College of Technology in Beaumont, Texas and his MSEE degree in Power Systems Engineering from the University of Pittsburgh. Elmo Price He began his career with Westinghouse in 1970 and worked in many engineering positions. He also worked as a district engineer located in New Orleans providing engineering support for Westinghouse power system products in the South-central U.S. With the consolidation of Westinghouse into ABB in 1988, Elmo assumed regional responsibility for product application for the Protective Relay Division. From 1992 to 2002 he worked in various technical management positions responsible for product management, product design, application support and relay schools. From 2002 to 2008 Elmo was a regional technical manager providing product sales and application support in the southeastern U.S. Elmo is currently senior consultant for ABB, a registered professional engineer and a Life Senior member of the IEEE. He is a member of the IEEE Power System Relay Committee and the Line Protection Subcommittee, serving as a contributing member to many working groups. He has two patents and has authored and presented numerous industry papers. © ABB Group October 7, 2014 | Slide 4 Learning objectives © ABB Group October 7, 2014 | Slide 5 Line distance measurement methods and characteristics Apparent impedance of fault loops and differences in phase and ground measurements The importance of faulted phase selection Step distance line protection Zone acceleration schemes (non-pilot) Basics of communications assisted schemes (optional – time permitting) Distance and impedance relays ~ © ABB Group October 7, 2014 | Slide 6 ZS VR IR ZL Uses both voltage and current to determine if a fault is within the relay’s set zone of protection Settings based on positive and zero sequence transmission line impedance Measures phase and ground fault loops Distance and impedance relays Brief History ~ © ABB Group October 7, 2014 | Slide 7 ZS VR IR ZL 1921 – Voltage restrained time overcurrent was first form of impedance relaying • 1929 – Balance beam impedance relay improved operating speed performance, but was non-directional • 1950 – Induction cup phase comparator providing mho distance characteristic • 1965 – Solid-state implementations • 1984 – Microprocessor implementations Impedance relay Simple balance beam ~ ZS VR IR ZR X ZR Restraint Torque VR R Operate Torque IR*ZR Reach to balance point = VR/IR = ZR © ABB Group October 7, 2014 | Slide 8 Distance relays Need Fault levels are higher on high voltage transmission lines Faults need to be cleared rapidly to avoid instability, and extensive damage Advantages © ABB Group October 7, 2014 | Slide 9 The impedance zone has a fixed impedance reach Greater Instantaneous trip coverage with security Greater sensitivity Easier setting calculations and coordination Fixed zone of protection that are relatively independent of system changes Higher independence of load Distance relay application ZR G ZG H ZH ZL Relay Relay ZH X H Impedance Plane ZR Operating Characteristic ZL R G ZG © ABB Group October 7, 2014 | Slide 10 Distance relay characteristics Impedance ZH X No operation region ZR Operate H ZL MTA R G 32 (Directional unit) © ABB Group October 7, 2014 | Slide 11 Distance relay characteristics Mho distance, self (fault voltage) polarized ZH X No Operation Region ZR H ZL Operate MTA G © ABB Group October 7, 2014 | Slide 12 R Distance relay characteristics Mho distance, (healthy) voltage polarized ZH X • ZR No Operation Region Typical polarizing Quantities H ZL Operate R ZG © ABB Group October 7, 2014 | Slide 13 G • Cross • Positive Sequence • Memory Distance relay characteristics Offset mho distance ZH X No operation region ZR H ZL Operate G Close-in faults © ABB Group October 7, 2014 | Slide 14 MTA R 32 (Directional unit) Distance relay characteristics Reactance ZH X No operation region XR ZR Operate ZL MTA G - XR © ABB Group October 7, 2014 | Slide 15 H Load supervision R R 32 (Directional unit) Distance relay characteristics Quadrilateral X No operation region ZH XR ZR ZL H Good resistance coverage Operate MTA G MTA R RR 32 (Directional unit) © ABB Group October 7, 2014 | Slide 16 Distance relay characteristics Switched zone quadrilateral No operation region X Zone-3 Operate Zone-2 Zone-1 © ABB Group October 7, 2014 | Slide 17 R Distance relay characteristics Mho distance with switched reactance X No operation region Zone-3 Zone-2 Zone-1 Operate © ABB Group October 7, 2014 | Slide 18 R Distance relay characteristics Lenticular No operation region ZH X H MTA G © ABB Group October 7, 2014 | Slide 19 Multi-phase faults R Phase comparators S1 S2 PHASE COMPARATOR S1 Compares the phase angle of two phasor quantities to determine operation © ABB Group October 7, 2014 | Slide 20 1/0 S2 OPERATE RESTRAIN Apply operating torque Apply opening torque Distance relay characteristics KD-10 cylinder unit (comparator) and compensator IA VA IB X CYLINDER UNIT ZR S1 XZY IC VC S2 VB © ABB Group October 7, 2014 | Slide 21 FZY Z ZR COMPENSATOR Y Phase-to-phase unit FXY Distance relay characteristics KD-10 cylinder unit Compensator IA - I B VAG VXY = VAB - (IA - IB)ZR (IA - IB)ZR X IC - IB FXY VXY VCG Z VCB (IC - IB)ZR VZY Y VBG © ABB Group October 7, 2014 | Slide 22 Cylinder unit VZY = VCB - (IC - IB)ZR FZY Trips when VXY leads VZY XZY sequence Distance relay characteristics Mho distance phase comparator principle Generic single phase self polarized without zero sequence compensation IX IX IZC – IZ IZC IZC - IZ IZC ß IZ IR V (a) Self (faulted phase) Polarized ZC = impedance reach setting Z = fault impedance Vf = fault voltage at relay I = fault current © ABB Group | Slide 23 ß > 90° S2 IZ October 7, 2014 ß < 90° IR V (b) Internal and External Fault S1 V f IZ S 2 IZ C V f IZ C IZ Trip b < 90O S1 Distance relay characteristics Mho distance phase comparator – cross polarized IX IZC - IZ IZC Generic single phase (healthy) voltage polarized without zero sequence compensation IZ V I(Z+ZS) IR IZS VS Z+ZS = fault impedance from source VS = source voltage © ABB Group October 7, 2014 | Slide 24 S1 I ( Z Z S );VBC , V1 , VMem S 2 IZ C IZ Distance relay characteristics Mho distance phase comparators VOP VPOL Zc*IXY - VXY jVXY XY = AB, BC, CA Zc = setting Zc*IXY - VXY VZ XY = AB, BC, CA Z = C, A, B Zc = setting VAB – (IA – IB)Zc Zc = setting VCB – (IC – IB)Zc Three units required for phase-to-phase and three-phase Self Polarizing No expansion Requires directional unit supervision Requires memory for zero voltage faults VOP leads VPOL Three units required for phase-to-phase and three-phase Cross Polarizing Source Impedance expansion Requires directional unit supervision Requires memory for zero voltage faults VOP leads VPOL Single unit required for phase-to-phase (AB, BC, CA) Separate unit required for three-phase faults Source Impedance expansion VOP leads VPOL Positive Sequence Polarizing, VPOL == sub jVZY with VX1 © ABB Group October 7, 2014 Comments | Slide 25 Distance relay characteristics Mho distance phase comparators Comments VOP VPOL VXG – Zc*(IX + K0I0) VZY X = A, B, C YZ = BC, CA, AB I0 = 1/3(IA+IB+IC) K0=(Z0 - Z1)/Z1 VXG – Zc*(IX + KNIR) jVZY X = A, B, C YZ = BC, CA, AB IR = IA+IB+IC KN = (Z0 - Z1)/3Z1 Three units required for phase-toground (A, B, C) zero sequence (I 0)compensation Cross Polarizing Source Impedance expansion Requires directional unit supervision VOP leads VPOL Three units required for phase-toground (A, B, C) Residual ground (I r=3I0) compensation Cross Polarizing Source Impedance expansion Requires directional unit supervision VOP leads VPOL Positive sequence polarizing, VPOL == sub jVZY with VX1 © ABB Group October 7, 2014 | Slide 26 Quadrilateral characteristics Reactance Lines (current polarization) S1 = IZC - V = (XC - Z)I q S2 = VPOL = XCI XC - Z XC Only the forward reach line can be defined, therefore, it must be directionally supervised S1 X ZC Z S2 q Z RC RF -XC q Operate q < ± 90O © ABB Group October 7, 2014 | Slide 27 I2 used for load compensation R Quadrilateral characteristics Resistance (current polarized) X S1 = IRCF - V = (RCF - Z)I S2 = VPOL = RCFI Z RCF S1 q S2 RCF - Z q RCF Z R Operate q < ± 90O © ABB Group October 7, 2014 | Slide 28 Distance relay characteristics Reference E. Price, T. Einarsson, “Complementary Approach for Reliable High Speed Transmission Line Protection,” 62nd Annual Georgia Tech Protective Relaying Conference, Atlanta, Georgia, 2008. © ABB Group October 7, 2014 | Slide 29 Apparent impedance of fault loops 6 fault loops measured for each zone AG BG CG Fault Types • Phase-to-ground • Phase-to-phase AB CA • Two phase-to-ground • Three phase BC © ABB Group October 7, 2014 | Slide 30 Apparent impedance of fault loops Three phase X ZL1 ZR1 IN = 0 ZLN MTA R Relay Phase Impedance Characteristic Apparent impedance phase) VA= IA ZL1 Z3P = ZL1 =VA/IA © ABB Group October 7, 2014 | Slide 31 (per ZL1 ZL1 Fault applied on line at ZL1 Phase reach is set in terms of positive sequence impedance, ZL1 Apparent impedance of fault loops Phase-to-phase ZL1 X ZL1 MTAP R Relay Phase-to-phase impedance characteristic Apparent impedance, ZPP VAB = (IA - IB ) ZL1 = 2IA ZL1 ZPP =ZL1 = VAB/(IA - IB ) = (VA - VB )/(IA - IB ) Phase reach is set in terms of positive sequence impedance, ZL1 © ABB Group October 7, 2014 | Slide 32 ZLN ZL1 ZL1 Apparent impedance of fault loops Phase-to-ground X Z L1 ZG = ZL1 + ZLN ZL1 MTAP ZLN MTAG ZL1 R Relay Phase-to-ground impedance characteristic Apparent impedance (no load IA = 3I0 ) VA = IA ZL1 + 3I0ZLN = IA (ZL1 + ZLN) ZG = VA /IA = (ZL1 + ZLN) © ABB Group October 7, 2014 | Slide 33 MTAG = Argument ( ZL1 + ZLN ) ZL1 Apparent impedance of fault loops Phase-to-ground Apparent impedance X Z L1 MTAP Arg(1+KN) ZG = (ZL1 + ZLN) ZLN = (ZL0 - ZL1) / 3 ZG = (2ZL1 + ZL0) / 3 (ground loop) MTAG R Relay Phase-to-ground impedance characteristic ZL1 with residual 3I0 compensation ZG = ZL1 ( 2 + ZL0 / ZL1) / 3 ZG = ZL1 ( 2 + 1 + ZL0 / ZL1 - 1 ) / 3 ZG = ZL1(1 + KN); KN = (ZL0 - ZL1)/3ZL1 MTAG = Arg( ZG) © ABB Group October 7, 2014 | Slide 34 Apparent impedance of fault loops Phase-to-ground Two Factors used by different relays and manufacturers Residual [neutral] current compensation KN compensates for 3I0 VA Z KN K0 compensates for I0 Ground reach is set in terms of ZL1 and KN: © ABB Group October 7, 2014 | Slide 35 K0 ZL0 - ZL1 I 3I 3ZL1 0 ZL0 - ZL1 3ZL1 VA Z Zero sequence current compensation L1 A L1 A ZL0 I I - 1 ZL1 0 ZL0 -1 ZL1 ZG = ZL1(1 + KN) Faulted phase selection Release or identify correct impedance loop A-B A-G B-C B-G C-A C-G 6 fault loops measured in each zone © ABB Group October 7, 2014 | Slide 36 Single pole trip Event recording Fault location Faulted phase selection Issues Multiple impedance loop operations for a fault event A-B A-G © ABB Group October 7, 2014 | Slide 37 B-C B-G C-A C-G • Common phases of a fault loop • Magnitude of fault quantities • Load • Fault resistance Faulted phase selection Issues The FF unit may operate for close-in reverse FF, FFG, or FG faults The FF unit may operate for close-in forward FG faults The FG units may operate for close-in reverse FG faults The FF unit of a non-faulted loop may operate for FFG faults with high fault resistance e.g. CA unit for a BCG fault The CA operation will occur with the expected BC operation giving the appearance of a three phase fault. These issues are resolved with directional and/or sequence current supervision. © ABB Group October 7, 2014 | Slide 38 Faulted phase selection Issues The FG unit of the leading phase will overreach for forward external FFG faults with any measurable fault resistance e.g. BG unit for a BCG fault The FG unit of the lagging phase will underreach for forward internal FFG faults near the reach setting with any measurable fault resistance e.g. CG unit for a BCG fault This is generally of no consequence These issues are the result of FFG faults and must be resolved by accurate phase selection. © ABB Group October 7, 2014 | Slide 39 Faulted phase selection Response of BG, CG and BC units to BCG fault 5 2 Fault Location in PU of Zone Reach Setting, Zc SIRz 3 1.5 Error Zone of FG units for FFG faults B BG is operated 1 0.5 Overreaching BG Units 1 BC Unit Underreaching CG Units Operates f or all parameters at 1.0 A 0.5 0.5 1 CG is operated 3 5 0 0 October 7, 2014 0.01 0.02 0.03 0.04 0.05 0.06 0.07 Per Unit Fault Resistance, Rg © ABB Group | Slide 40 0.08 0.09 0.1 Faulted phase selection Reference E. Price, T. Einarsson, “The Performance of Faulted phase Selectors used in Transmission Line Applications,” 62nd Annual Georgia Tech Protective Relaying Conference, Atlanta, Georgia, 2008. © ABB Group October 7, 2014 | Slide 41 Application Location of cts and vts © ABB Group October 7, 2014 | Slide 42 Reach of a distance relay is measured from the location of the voltage transformer Directional sensing occurs from the location of the current transformer In most applications vts and cts are usually at same location (no measurable impedance between them) Their location should always be considered especially for applications with transmission lines terminated with transformers Application Step distance protection T3 T2 T1 Z3 Z2 Z1 G H Z1 Z3 © ABB Group October 7, 2014 | Slide 43 Z2 T1 T2 T3 Zone 1 set for 80 - 90 % of line impedance Zone 2 set for 100% of line plus 25 - 50% of shortest adjacent line from remote bus Zone 3 set for 100% of both lines plus 25% of adjacent line off remote bus Step distance protection Zone 1 T3 T2 T1 Z3 Z2 Z1 G H Z1 Z3 © ABB Group October 7, 2014 Z2 T1 T2 T3 Do not want Zone 1 to reach beyond remote bus 10 to 20% is safety factor Inaccuracies Relays Current and potential transformers Line impedances | Slide 44 Step distance protection Zone 2 T3 T2 T1 Z3 Z2 Z1 G H Z1 Z3 © ABB Group October 7, 2014 | Slide 45 Z2 T1 T2 T3 H Z1 R Operates through a timer (T2) Timer set for Coordination Time Interval (CTI) that allows remote relay zone 1 [Z1] and breaker [at H] to operate with margin before zone 2 [Z2] relay Z2 at G must overreach the remote bus H, but should not overreach the closest far bus at R Z2 at G is remote backup to Z1 at H Step distance protection Zone 3 T3 T2 T1 Z3 Z2 G H Z1 Z3 © ABB Group October 7, 2014 | Slide 46 Z2 R Z1 H Z1 Z2 T1 T2 T3 Operates through a timer (T3) Timer set for Coordination Time Interval (CTI) that allows remote relay zone 2 [Z2] and breakers [at H and R] to operate with margin before the zone 3 [Z3] relay Z3 at G is also remote backup to Z1 and Z2 at H Step distance protection Zone 3 T2 T3 Z3 T1 Z1 R Z2 Z1 G H Z1 Z2 © ABB Group | Slide 47 T1 T2 Zone 3 relay [Z3] may be applied looking reverse for pilot system logic with no timer Zone 3 relay [Z3] may be applied looking reverse for reverse [backup] bus protection October 7, 2014 T3 Timer set to allows reverse zone 1 [Z1] relay and breaker [at G] to operate with margin before zone 3 [Z3] relay Step distance protection Operating time profile Z3 Z2 Z1 T3 T2 21/67 (Impedance controlled directional TOC) Z2 Z2 Z1 © ABB Group October 7, 2014 | Slide 48 Z1 Step distance protection Infeed [from remote bus] Z2 Z1 G IG IIN © ABB Group October 7, 2014 | Slide 49 Reduces the apparent reach measured by distance relays Depends on the ratio between current going through relay (IG) and current from infeed (IIN) Usually not a factor on Zone 1 [Z1] relay unless tapped line [or appreciable fault resistance for ground faults] Zone 2 may underreach remote bus Step distance protection Infeed [from remote bus] Z2 VG ZG G G IG IIN ZH IG+ IIN H With Zero voltage fault and Z2 = ZG + ZH VG = IGZG + ( IG + IIN ) ZH ZA (Apparent) = VG / IG ZA = ZG + (1 + IIN/IG) ZH ZA = ZG + ZH + (IIN/IG)ZH (Increase in Apparent Impedance) Z2 must be set to overreach bus H for infeed at bus H and not overreach bus K for no infeed at bus H © ABB Group October 7, 2014 | Slide 50 K Step distance protection Outfeed Z1 = 2.5 W G 1W 2W 2a 1a 1W 1a 1W 1a Usually associated with three terminal line applications and paralleling of line segment Example: VG = 2(1) + 2(1 ) = 4 ZG (Apparent) = VG / IG ZG = 4/2 = 2 W Z1 will overreach and see the fault © ABB Group October 7, 2014 | Slide 51 Step distance protection Tapped transformers and loads m mZL G IG ZT (1-m)ZL IH IG + IH VG = IGmZL + ( IG + IH ) ZT ZG (Apparent) = VG / IG ZG = mZL + (1 + IH/IG) ZT ZG = mZL + ZT + IH/IGZT (Increase in apparent impedance) Apparent impedance will always be larger than impedance to fault © ABB Group October 7, 2014 | Slide 52 Step distance protection Lines terminated into transformers ZT IL ZL IH VL VH IH and VH preferred to provide line protection Use of VL and/or IL affects measured impedance and requires ct and/or vt ratio adjustment Transformer should always be protected separately Reference E. Price, R. Hedding, “Protecting Transmission Lines Terminated into Transformers,” 63nd Annual Georgia Tech Protective Relaying Conference, Atlanta, Georgia, 2009. © ABB Group October 7, 2014 | Slide 53 Source impedance ratio Ratio of source impedance to the line impedance SIR to the relay is the ratio of source impedance to the zone impedance setting The higher the SIR the more complex the line protection with zone 1 Measurement errors are more pronounced © ABB Group October 7, 2014 | Slide 54 Current and or voltage transformer error CVT transients Zone-1 may not be recommended in many applications Current differential protection preferred Source impedance ratio Recommended applications Short Line Current Differential Phase Comparison Pilot (POTT, DCB) Medium Line Above Step Distance Long Line SIR > 4.0 4.0 > SIR > 0.5 0.5 > SIR Above Step Distance IEEE Guide for Protective Relay Applications to Transmission Lines - IEEE Std C37.113-1999 © ABB Group October 7, 2014 | Slide 55 Non-pilot applications Zone 1 extension Z1 Z1 Z1 A © ABB Group October 7, 2014 | Slide 56 B C Z1 F D Z1 reach is initially set to overreach remote bus Circuit breakers controlled by relays A, C, & D trip for a fault at F Z1 reach is reduced to not overreach remote bus High-speed reclose Non-pilot applications Zone 1 extension Z2 Z1 Z1 Z1 Z1 A © ABB Group | Slide 57 C F D After high-speed reclose October 7, 2014 B Circuit breaker controlled by relay C trips instantaneously Circuit breaker controlled by relay D trips time-delayed Circuit breaker controlled by relay A does not trip Non-pilot applications Load loss trip Z2 Z2 Z1 Z1 A © ABB Group | Slide 58 F B Unbalanced fault occurs at F Breaker controlled by relay B trips instantaneously by Z1 Balanced load current, IL, is interrupted LLT Logic at A October 7, 2014 IL Detects loss of balanced (load) current and bypasses Z2 timer to trip Does not operate for three-phase fault Switch onto fault logic ZSOTF I CLOSING A Breaker position Dead line logic When breaker controlled by relay A closes SOTF asserts when: I and Not V, and/or ZSOTF operates © ABB Group October 7, 2014 | Slide 59 B Logic determines breaker has been open awhile and sets SOTF logic (aka: CIFT, SOFT) V OPEN Set ZSOTF offset, overreaching line and below minimum load impedance Stub bus protection logic © ABB Group October 7, 2014 | Slide 60 Pilot relaying schemes Communication assisted schemes Goal - High speed simultaneous tripping of all line terminals for internal line faults STATION C A STATION D X B P&C STATION E P&C C P&C © ABB Group October 7, 2014 | Slide 61 Pilot relaying schemes Communication assisted schemes Goal - High speed simultaneous tripping of all line terminals for internal line faults STATION C A STATION D X B P&C STATION E P&C C COMMUNICATIONS P&C Requires reliable high-speed communications between line terminals. © ABB Group October 7, 2014 | Slide 62 Pilot Communications Power Line Carrier (PLC) The communication signal is coupled to the transmission line being protected requiring additional substation equipment Line traps Line tuners Coupling capacitors On/Off Keying, Frequency Shift Keying (FSK) Generally more available and economical than other forms of pilot communications Communication issues tend to occur when reliable communications is need most – during the fault DCB (On/Off) and DCUB (FSK) developed specifically for PLC 63 Pilot Communications Non Power Line Carrier 64 The communication signal is routed separately from the transmission line conductor Audio tone – FSK over voice (telephone, microwave) Digital – most reliable, particularly with fiber optics, direct connected or multiplexed Directional Comparison Directional Comparison relaying determines the fault direction at each line terminal and compares the results to determine the fault to be internal or external to the protected line. FWD Element (FP-A)à INTERNAL FAULT FINT A ßFWD Element (FP-B) STATION C FWD Element (FP-A)à EXTERNAL FAULT A STATION C 65 B STATION D STATION D B FEXT REV Element (RP-B)à Distance Protection Directional Comparison Schemes Non PLC Channels DUTT* – Direct-underreaching transfer trip POTT – permissive-overreaching transfer trip PUTT – permissive-underreaching transfer trip PLC DCB – directional comparison blocking DCUB – directional comparison unblocking * Although there is no directional comparison between terminals this scheme is usually considered with directional comparison schemes. 66 DUTT – Direct-underreaching Transfer Trip STATION D STATION C A B FINT 21-1 21-1 Must Overlap Comm Tx Rx Rx [f1 from B] 21-1 (A) TRIP A OR Tx [f1 to TRIP B] Also known as an “Intertrip” scheme 67 Tx Rx f1 Comm Rx [f1 from A] 21-1 (B) Underreaching Distance Relay OR TRIP B Tx [f1 to TRIP A] DUTT – Direct-underreaching Transfer Trip Advantages Fast method for clearing end zone faults Single communications channel Disadvantages 68 Cannot protect full line if one terminal is open or has weak infeed Requires ground distance relays for accurate reach on ground faults (no overcurrent) Subject to 21-1 overreaching issues (e.g. ccvt transients) Spurious communication channel noise may cause undesired trip (secure channel desired – FSK, digital) PUTT – Permissive-underreaching Transfer Trip STATION D STATION C A B Must Overlap 21-1 FINT 21-1 Overreaching Distance Relay Underreaching Distance Relay 21-2 21-2 Comm Tx Rx Rx [f1 from B] 21-2 (A) 21-1 (A) AND Tx Rx f1 TRIP A Tx [to B] Comm Rx [f1 from A] 21-2 (B) 21-1 (B) Rx signal should have a minimum receive time to allow operation of 21-2. 69 TRIP B AND Tx [f1 to A] PUTT – Permissive-underreaching Transfer Trip Advantages More secure than DUTT requiring a 21-2 operation for permission to trip Single communications channel Disadvantages 70 Cannot protect full line if one terminal is open or has weak infeed Requires ground distance relays for accurate reach on ground faults (no overcurrent) POTT – Permissive-overreaching Transfer Trip STATION D STATION C A B FINT FP-A Overreaching Distance FP-B and OC Relays: 21-2, 21N-2, 67N Comm Tx Rx Rx [f2 from B] FP-A AND f1 TRIP A f2 Tx Rx Comm Rx [f1 from A] FP-B AND Tx [f1 to B] Rx signal should have a minimum receive time to allow operation of 21-2. 71 TRIP B Tx [f2 to A] POTT – Permissive-overreaching Transfer Trip Advantages More dependable than PUTT because it sees all line faults. Open terminal and weak-end infeed logic can be applied. Forward and reverse ground directional overcurrent relays may be applied for greater sensitivity to high resistance ground faults Disadvantages Requires a duplex communications channel (separate frequency/signal for each direction) Will not trip for internal fault with loss of channel (but usually applied with a zone-1/2 step-distance relay) 72 Directional Comparison Blocking (DCB) and Unblocking (DCUB) DCB and DCUB schemes are specifically intended to be used with systems where communications is less secure (likely to be lost) during line fault conditions Power-line carrier – signal communications is on same conductor that you are protecting STATION C STATION D A Transmission Line B Power Line Carrier Channel Relay 73 Relay The PLC Channel Station A Bus Signal: 30 to 500 kHz 1 to 100 Watts (7 to 70 V rms) Line Trap Fault 2 1 Signal Path Switchyard Control House Protective Relay System T Relay PT inputs Coaxial Cable Coupling Capacitor Voltage Transformer (ccvt) H R Drain Coil Line Tuner DCUB – Directional Comparison Unblocking fB1 and fB2 are continuous block signals until a fault is detected and the frequency is shifted to the unblock (trip) f1 and/or f2. 75 DCUB – Directional Comparison Unblocking Advantages Very secure at it requires receipt of Unblock signal for tripping. Has logic to handle loss of channel during faults. Open terminal and weak-end infeed logic can be applied. Forward and reverse ground directional overcurrent relays may be applied for greater sensitivity to high resistance ground faults Security logic for loss of channel (carrier holes) only delays trip during loss of channel Disadvantages 76 Requires a duplex communications channel (separate trip and guard frequencies for each direction) DCB – Directional Comparison Blocking 77 DCB – Directional Comparison Blocking Advantages Very dependable – does not depend on channel for tripping for internal faults Open terminal and weak-end infeed are handled by scheme Forward and reverse ground directional overcurrent relays may be applied for greater sensitivity to high resistance ground faults Low cost communications channel – single frequency channel On/Off PLC Disadvantages Not as secure – tends to overtrip for slow channel or loss of channel Security logic for carrier holes may be required – slows tripping. Channel is normally off so periodic checking is required 78 References © ABB Group October 7, 2014 | Slide 79 1. IEEE Guide for protective Relay Applications to Transmission Lines, IEEE Std. C37-113, 1999. 2. W. A. Elmore, Protective Relaying: Theory and Application, Marcel Decker, Inc., New York,1994. Relion® REL650/670 Advancing Line Distance Protection For maximum reliability of your power system REL650 The best choice for subtransmission applications REL670 Optimized for transmission applications Achieve significant savings in configuration and commissioning with efficient system integration and optimum “off-the-shelf” solutions and settings Do more with less - the advanced logic and multipurpose functionality allow you to customize protection schemes for multiple objects with a single IED Protect your investment with unrivalled sensitivity, speed and the best possible protection for power transformer winding turn-to-turn faults Maximize flexibility and performance with powerful application and communication capabilities that allow you to integrate these IEDs into new or retrofit substation automation systems or use them as stand-alone multifunctional units This webinar brought to you by: ABB Power Systems Automation and Communication • Relion Series Relays – Advanced flexible platform for protection and control • RTU 500 Series – Proven, powerful and open architecture • MicroSCADA - Advanced control and applications • Tropos – Secure, robust, high speed wireless solutions We combine innovative, flexible and open products with engineering and project services to help our customers address their challenges. Thank you for your participation Shortly, you will receive a link to an archive of this presentation. To view a schedule of remaining webinars in this series, or for more information on ABB’s protection and control solutions, visit: www.abb.com/relion © ABB Group October 7, 2014 | Slide 82
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